A display device including a display panels such as a liquid crystal panel is used for a portable terminal device such as a mobile phone and PDA or an electronic device such as a computer and a television. A parallax barrier is applied to such a display device to display a stereoscopic image. Using a parallax barrier, each of a left eye and a right eye sees a different image and human beings sense a stereoscopic image due to binocular parallax. Patent Document 1 discloses one example of such a display device having a function of displaying stereoscopic images.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-272354